Shape memory polymer foams for endovascular therapies

ABSTRACT

A system for occluding a physical anomaly. One embodiment comprises a shape memory material body wherein the shape memory material body fits within the physical anomaly occluding the physical anomaly. The shape memory material body has a primary shape for occluding the physical anomaly and a secondary shape for being positioned in the physical anomaly.

CROSS-REFERENCE TO RELATED APPLICATION

This application is a Continuation of co-pending patent application Ser.No. 13/010,036 filed Jan. 20, 2011, which claims priority to and is aContinuation of U.S. patent application Ser. No. 10/801,355 filed Mar.15, 2004, now U.S. Pat. No. 8,133,256 and entitled, “Shape MemoryPolymer Foams for Endovascular Therapies”, which claims priority to U.S.Patent Application No. 60/508,808 filed Oct. 2, 2003. The content ofeach of the above files is hereby incorporated by reference.

STATEMENT AS TO RIGHTS TO INVENTIONS MADE UNDER FEDERALLY SPONSOREDRESEARCH AND DEVELOPMENT

The United States Government has rights in this invention pursuant toContract No. DE-AC52-07NA27344 between the United States Department ofEnergy and Lawrence Livermore National Security, LLC for the operationof Lawrence Livermore National Laboratory.

BACKGROUND

1. Field of Endeavor

The present invention relates to Endovascular Therapies and moreparticularly to Shape Memory Polymer Foams for Endovascular Therapies.

2. State of Technology

United States Patent Application 2003/0144695 by James, F. McGuckin andRichard T. Briganti, published Jul. 31, 2003, and United States PatentApplication 2003/0009180 by Peter W. J. Hinchliffe, James, F. McGuckin,Richard T. Briganti, and Walter H. Peters, published Jan. 9, 2003, for avascular hole closure device provides the following state of thetechnology information, “During certain types of vascular surgery,catheters are inserted through an incision in the skin and underlyingtissue to access the femoral artery in the patient's leg. The catheteris then inserted through the access opening made in the wall of thefemoral artery and guided through the artery to the desired site toperform surgical procedures such as angioplasty or plaque removal. Afterthe surgical procedure is completed and the catheter is removed from thepatient, the access hole must be closed. This is quite difficult notonly because of the high blood flow from the artery, but also becausethere are many layers of tissue that must be penetrated to reach thefemoral artery.”

United States Patent Application 2002/0133193 published Sep. 19, 2002,and U.S. Pat. No. 6,391,048 issued May 21, 2002, to Richard S. Ginn andW. Martin Belef, for an integrated vascular device with puncture siteclosure component and sealant and methods of use provides the followingstate of the technology information, “Catheterization and interventionalprocedures, such as angioplasty and stenting, generally are performed byinserting a hollow needle through a patient's skin and muscle tissueinto the vascular system. A guide wire then is passed through the needlelumen into the patient's blood vessel. The needle is removed and anintroducer sheath is advanced over the guide wire into the vessel. Acatheter typically is passed through the lumen of the introducer sheathand advanced over the guide wire into position for a medical procedure.The introducer sheath therefore facilitates insertion of various devicesinto the vessel while minimizing trauma to the vessel wall andminimizing blood loss during a procedure. Upon completion of the medicalprocedure, the catheter and introducer sheath are removed, leaving apuncture site in the vessel. Commonly, external pressure is applieduntil clotting and wound sealing occurs. However, this procedure is timeconsuming and expensive, requiring as much as an hour of a physician'sor nurse's time, is uncomfortable for the patient, and requires that thepatient be immobilized in the operating room, cathlab, or holding area.Furthermore, a risk of hematoma exists from bleeding prior tohemostasis.”

U.S. Pat. No. 6,174,322 issued Jan. 16, 2001 to Bernhard Schneidt for anOcclusion device for the closure of a physical anomaly such as avascular aperture or an aperture in a septum provides the followingstate of the technology information, “The human circulatory system iscomprised of a cardiovascular circulation and pulmonary circulation. Inthe embryonic phase of the development of a human being, the twocirculatory systems are joined by the ductus arteriosus. The ductusconnects the aorta (systemic circulation) with the pulmonary artery(pulmonary circulation). In the normal development of an infant, thisductus closes after birth. In pathological development, the ductus maynot close so that the two circulatory systems remain connected evenafter birth. This can reduce the life expectancy of the infant. Closureof the ductus by means of a surgical procedure is well-known. However,this procedure is very cost-intensive and is connected with a risk forthe patient. Closure of the ductus by means of an IVALON® (polyvinylalcohol) foam plug (Porstmann method) is also well-known. In this case,a guide rail is introduced via a femoral vein into the aorta, throughthe ductus into the pulmonary artery and from there through the rightventricle and the right atrium and finally to the outside again via theopposite femoral vein. The ductus plug is then pushed into the ductuswhere it is “jammed in place.” Owing to the high pressure differentialbetween the aorta and pulmonary artery, high demands are placed on thefixation of the ductus plug within the ductus.”

SUMMARY

Features and advantages of the present invention will become apparentfrom the following description. Applicants are providing thisdescription, which includes drawings and examples of specificembodiments, to give a broad representation of the invention. Variouschanges and modifications within the spirit and scope of the inventionwill become apparent to those skilled in the art from this descriptionand by practice of the invention. The scope of the invention is notintended to be limited to the particular forms disclosed and theinvention covers all modifications, equivalents, and alternativesfalling within the spirit and scope of the invention as defined by theclaims.

The present invention provides a system for occluding a physicalanomaly. One embodiment of the present invention comprises a shapememory material body wherein the shape memory material body fits withinthe physical anomaly occluding the physical anomaly. The shape memorymaterial body has a primary shape for occluding the physical anomaly anda secondary shape for being positioned in the physical anomaly. In oneembodiment, the shape memory material body comprises a shape memorypolymer. In another embodiment, the shape memory material body comprisesa shape memory polymer foam.

One embodiment of the present invention comprises a method for occludinga physical anomaly. The method comprises the steps of providing a shapememory material body with a secondary shape for being positioned in theinterior of the physical anomaly and a larger primary shape foroccluding the anomaly, positioning the shape memory material body in theinterior of the physical anomaly when the shape memory material body isin the secondary shape, and causing the closure body to change to thelarger primary shape for occluding the anomaly. In one embodiment, thestep of providing a shape memory material body with a secondary shapefor being positioned in the interior of the physical anomaly and alarger primary shape for occluding the anomaly comprises providing ashape memory polymer foam body with a secondary shape for beingpositioned in the interior of the physical anomaly and a larger primaryshape for occluding the anomaly.

One embodiment of the present invention comprises a system for occludinga physical anomaly. The embodiment comprises a shape memory materialbody means for occluding the anomaly, the shape memory material bodymeans having a secondary shape for being positioned in the interior ofthe physical anomaly and a larger primary shape, means for positioningthe shape memory material body in the interior of the physical anomalywhen the shape memory material body is in the secondary shape, and meansfor causing the shape memory material body to change to the largerprimary shape for occluding the anomaly. In one embodiment, the shapememory material body means comprises a shape memory polymer body with asecondary shape for being positioned in the interior of the physicalanomaly and a larger primary shape for occluding the anomaly. In anotherembodiment, the shape memory material body means comprises a shapememory polymer foam body with a secondary shape for being positioned inthe interior of the physical anomaly and a larger primary shape foroccluding the anomaly.

The invention is susceptible to modifications and alternative forms.Specific embodiments are shown by way of example. It is to be understoodthat the invention is not limited to the particular forms disclosed. Theinvention covers all modifications, equivalents, and alternativesfalling within the spirit and scope of the invention as defined by theclaims.

BRIEF DESCRIPTION OF THE DRAWINGS

The accompanying drawings, which are incorporated into and constitute apart of the specification, illustrate specific embodiments of theinvention and, together with the general description of the inventiongiven above, and the detailed description of the specific embodiments,serve to explain the principles of the invention.

FIG. 1 illustrates an embodiment of the present invention that providesa system for occluding a physical anomaly.

FIG. 2 is another view of the embodiment of the present invention shownin FIG. 1.

FIG. 3 illustrates an example of SMP foam actuator.

FIG. 4 illustrates a system for optical heating using optic fibers totransport light energy to the SMP actuator.

FIG. 5 illustrates an embodiment of a foam device system.

FIG. 6 illustrates another embodiment of a foam device system.

FIG. 7 illustrates another embodiment of a foam device system.

FIG. 8 illustrates another embodiment of a foam device system.

FIG. 9 shows collapsed SMP foam device.

FIG. 10 shows an expanded SMP foam device.

FIG. 11 shows embodiments of the distal ends of guidewires.

FIG. 12 illustrates another embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

Referring now to the drawings, to the following detailed description,and to incorporated materials, detailed information about the inventionis provided including the description of specific embodiments.

The present invention provides a system for occluding a physicalanolmaly. Various embodiments are contemplated. For example, oneembodiment provides a system for treating an arteriovenous malformation.In this embodiment a shape memory device is transferred into thearteriovenous malformation. The shape memory device is actuatedexpanding it inside the arteriovenous malformation and occluding thearteriovenous malformation.

In the general application, a vascular anomaly is treated using thedevice with the intent of stabilizing the anomaly from further expansionand possible rupture. The device is delivered endovascularly to the sitefor therapy via a catheter. The catheter may be previously placed usinga conventional guidewire or the device may be installed using theguidewire. Once the catheter is placed near the therapeutic site, thedevice is placed into the anomaly with the guidewire and guided visuallyby radiology. The device is then held in place and the foam is actuatedto expand, filling the anomaly. Once expanded, the foam will stay inplace on its own or an additional aid will be used to hold it in place;for example, a diaphragm for the aneurysm or a stent for the AVM. Thefoam is released from the guidewire or catheter via the expansionprocess or following actuation by known techniques. The guidewire and/orcatherer is then retracted and the therapy is completed. Should there bea misplacement of the foam, retrieval is possible using anothershape-memory polymer device or other conventional techniques.

Shape-memory materials have the useful ability of being formable into aprimary shape, being reformable into a stable secondary shape, and thenbeing controllably actuated to recover their primary shape. Both metalalloys and polymeric materials can have shape memory. In the case ofmetals, the shape-memory effect arises from thermally induced solidphase transformations in which the lattice structure of the atomschanges, resulting in macroscopic changes in modulus and dimensions. Inthe case of polymeric materials, the primary shape is obtained afterprocessing and fixed by physical structures or chemical crosslinking.The secondary shape is obtained by deforming the material while is anelastomeric state and that shape is fixed in one of several waysincluding cooling the polymer below a crystalline, liquid crystalline,or glass transition temperature; by inducing additional covalent orionic crosslinking, etc.

While in the secondary shape some or all of the polymer chains areperturbed from their equilibrium random walk conformation, having acertain degree of bulk orientation. The oriented chains have a certainpotential energy, due to their decreased entropy, which provides thedriving force for the shape recovery. However, they do not spontaneouslyrecover due to either kinetic effects (if below their lower Tg) orphysical restraints (physical or chemical crosslinks). Actuation thenoccurs for the recovery to the primary shape by removing that restraint,e.g., heating the polymer above its glass transition or meltingtemperature, removing ionic or covalent crosslinks, etc. Other types ofpolymers which undergo shape memory behavior due to photon inducedconformational transformations, conformational changes (e.g., rod-coiltransition) due to changes in chemical environment (pH, ionic strength,etc.), or structural changes due to imposed fields (e.g., electric,magnetic, . . . ) may also be used. Both shape memory alloys (SMAs) andshape memory polymers (SMPs) can be used for the shape memory materialof the present invention.

A shape memory material therapeutic device has advantages over existingtherapeutic devices of being able to be moved more easily through thecatheter to the point of placement, A shape memory material therapeuticcan be placed more precisely within the geometry of the vasculardisorder, and there is a higher degree of control over the expansionprocess while the device was being held in the desired position. A shapememory material therapeutic can be controllably expanded while beingheld in precise placement. A shape memory material therapeutic expandsto its secondary shape within a few seconds, which is much faster thancurrent expandable hydrogel based devices. The modulus of the devicescan be accurately controlled so that expansion forces are low and nodamage is done to areas of the vascular lumen.

The shape memory material device is expandable from 100% to 10000% byvolume. The shape memory material device is actuated by one of severalmeans including electromagnetic energy delivered optically. The shapememory material device is used to occlude part or all of a lumen,aneurysm, artiovascular malformation, or other physical anomaly.

The present invention also provides a process for making SMP foams withspecific pore structures; geometric shaping of the SMP device to fitspecific physiological geometries; the coating of the surface of the SMPto enhance biocompatibility and promote integration into the body; thedevelopment of a complete therapeutic device for aneurysm (and AVM)treatment which includes techniques to ensure proper placement anddevice designs and techniques to remove devices which have beenimproperly placed.

Referring now to FIGS. 1 and 2, two figures will be used to describe anembodiment of the present invention that provides a system for occludinga physical anolmaly. The embodiment is designated generally by thereference numeral 100. FIGS. 1 and 2 are schematic illustrations of theworking end of a system 100 for treating an arteriovenous malformationor aneurysm 102.

As shown in FIG. 1, a collapsed SMP foam device 105 is connected at theend of a guide wire 104. The SMP foam device 105 is placed inside theaneurysm 102. This is accomplished by delivering the SMP foam device 105through a catheter 103 using the guide wire 104. The catheter 103 isinserted through the artery 101 to position the SMP foam device 105 inthe aneurysm 102.

Referring now to FIG. 2 the SMP foam device 105 is shown actuated,thereby expanding it inside the aneurysm 102 and occluding the aneurysm102. The SMP foam device 105 is expandable from 100% to 10000% involume. The SMP foam device 105 is actuated by one of several meansincluding electromagnetic energy delivered optically. The SMP foamdevice 105 is used to occlude part or all of a lumen, aneurysm, orartiovascular malformation. The expanded SMP foam device 105 isreleasing from the end of the guide wire 104. The guide wire 104 is thenretracted through the catheter 103. The catheter 103 is then retractedfrom the artery 101.

The SMP foam device 105 is made out of “shape memory polymer” (SMP). TheSMP is a material which can be formed into a specific “primary” shape,reformed into a “secondary” stable shape, then controllably actuated sothat it recovers its primary shape. The SMP device 105 has the structureof an open cell foam with porosity, pore size, and size distributionsdesigned for each individual application.

The general concept behind the SMP foam device for aneurism therapy willbe summarized with reference to FIGS. 1 and 2. The device consists of anSMP foam actuator 105 on the distal end, which is connected to thedistal end of a catheter 103 or alternatively the distal end of aguide-wire assembly 104. The catheter 103 or guide wire 104 contains anoptic fiber or alternative means to heat or radiate the SMP 105 foractuation. There is a coupling between the SMP foam 105 and the guidewire 103 which can be selectively disengaged. The SMP foam device 105 ismade of a suitable biocompatible SMP, is loaded with a radiopagueadditive, contains a laser dye suitable for vascular use, and is coatedwith a thrombogenic material such that upon actuation the large surfaceof the foam promotes rapid thrombus formation within the geometry of thefoam and adhesion of the foam to the aneurysm wall. The foam device 105can be made in a number of standard geometries for aneurysm, AVM, orvascular anomalies. For each use, a pre-made foam geometry is chosenwhich best fits the therapeutic need.

The present invention has uses wherever it is desirable to occlude aphysical anomaly. For example, the present invention has use for theclosure of an aneurysm for the prevention and/or treatment of a stroke.

Stroke is a major cause of mortality and the primary cause of long-termdisability in the United States. Each year there are an estimated700,000 occurrences of stroke, from which 150,000 people die and 400,000are left with a significant deficit. The costs of caring for victims ofstroke in the acute phase, for chronic care, and lost productivityamount to an estimated $40 billion per year. Approximately 20% ofstrokes are hemorrhagic and result from the rupture of eitherarteriovenous malformations (AVMs) or aneurysms. For aneurysm/AVMrupture, the incidence of death is about 29%, and an additional 20 to30% of patients suffer neurologic deficits. Since an estimated 4% ofaneurysm/AVMs rupture each year, a significant number of people (up to3.5 million) have aneurysm/AVMs for years prior to stroke occurrence,indicating significant benefit from early preventative treatment.

There are three treatment modalities for neurovascular aneurysm/AVMs;namely, standard microsurgery, the introduction of agents which occludeparts or all of the aneurysm/AVM, and radio surgery. At present, thehighest success rates are achieved using standard microsurgery in whichthe aneurysm/AVM is removed. However, microsurgery involves a great dealof trauma (cutting a hole in the skull), long recovery times, and can'tbe used for a significant minority of aneurysm/AVMs due to insufficientaccess or patient refusal. Radiosurgery involves applying a focused beamof radiation to vessel walls, resulting in shrinkage of theaneurysm/AVM. Radiosurgery is limited though to use in aneurysm/AVMswhich are relatively small in size and carries with it the risk ofdamage to surrounding brain tissue.

An emerging modality is the endovascular introduction of occluding gluesor metal coils for aneurysm/AVM stabilization and to promote healing.However, endovascular therapy based on current devices and materialsresults in cure rates of only 5-10% and carries a 3-5% risk of seriouscomplications; these include adhesion of the catheter to theaneurysm/AVM, glue or solvent toxicity, escape of material creatingembolic events downstream from the aneurysm/AVM, and aneurysm/AVMrupture.

The current FDA-approved endovascular procedure for treating aneurysmsis the GDC (Guglielmi Detachable Coil-Target Therapeutics, Fremont, CA).The embolic coils are delivered through an interventional guide catheterinto the aneurysm. The guide catheter generally enters through thefemoral artery and is then negotiated through the cardiovasculature intothe cerebrovasculature. A typical guide catheter is the Tracker 18 fromTarget Therapeutics with a 0.018 inch (approximately 450 μm) workingchannel for delivering therapeutic devices. The tip of the guidecatheter is placed in the aneurysm through the neck of the aneurysmusing fluoroscopic (x-ray) image guidance. Successive coils aredeposited such that they fill the volume of the aneurysm, resulting inreduced/eliminated blood flow in the aneurysm and, in turn, a greatlyreduced risk of acute stroke. Once the blood flow in the aneurysm hasbeen stopped, the body generally seals off the aneurysm resulting incomplete patient recovery with no risk of hemorrhagic stroke. Therapyutilizing the GDC has a number of limitations including a long proceduretime required to place several coils, the large mismatch between themechanical properties of the coil and the vascular wall, and thepossibility of a coil escaping from the aneurysm/AVM and lodgingdownstream, causing an embolic event.

SMP actuators are made of any polymeric material that exhibits ashape-memory effect and is suitable for use in this application. Thisincludes:

Thermoplastic SMPs—thermoplastic polymers are those which can be heatedinto a melt state in which all prior solid shape memory has been lost,processed into a shape, and solidified. If need be they can be re-heatedto their melt state and re-processed a number of times. In thermoplasticSMPs, the shape memory effect generally relates to the material having amultiphase structure in which the different phases have differentthermal transitions, which may be due to glass transitions, crystallinemelting points, liquid crystal-solid transitions, ionomeric transitions,etc. The primary shape is obtained by processing in the melt state abovethe highest transition temperature and then cooling to a temperature inwhich either a hard phase or other physical crosslink is formed to lockin that shape. The secondary shape is obtained by bringing the materialto a temperature above its actuation temperature but below its meltingtemperature, mechanically shaping the material into its secondary shape,then cooling it below its actuation temperature. Suitable thermoplasticSMPs include block copolymers (linear di, tri, and multiblocks;alternating; graft), immiscible polymer blends (neat and with couplingagents such as di or tri-block copolymers), semi-crystalline polymers,and linear polymers with ionomeric groups along the chain or grafted tothe chain.

Thermosetting SMPs—thermosetting polymers are those which are processedinto a part and simultaneously chemically crosslinked, so that the partis essentially one macromolecule. They cannot be re-processed bymelting. In thermosetting SMPs the primary shape is obtained during theinitial processing step involving crosslinking. The secondary shape isobtained by mechanically reshaping the material at a temperature orcondition in which the material is in an elastomeric state. Thissecondary shape is locked in by cooling the material below the actuationtemperature, which relates to a transition as described above. Suitablethermosetting SMPs include all of the types of materials described underthermoplastic SMPs but which can also be chemically crosslinked to formthe primary shape. In addition, crosslinked homopolymers can also beused as SMPs with the actuation temperature typically being the glasstransition temperature of the material.

Coil-rod transition SMPs are also used for the shape memory materialactuator. Some polymers undergo a coil to rod transition in their chainconformation by relatively small changes in their environment, such assolvent changes or changes in the ionic character in an aqueousenvironment. Similarly, adsorption of electromagnetic radiation of aspecific wavelength can cause changes in the conformation of certainpolymers, which induces a macroscopic shape response. Both thermoplasticand thermosetting polymers which undergo such rod-coil transitions canbe used for this application.

While all shape memory polymer compositions are suitable for the currentinvention, the compositions having the following properties areparticularly suitable: (1) Transparency—this usually is a characteristicof an SMP which is two phase but with microphase sizes below about 50microns, an SMP which is single phase and whose primary shape is fixedby covalent or ionic crosslinking, or a multiphase system in which allphases have very similar refractive indices. (2) The lowest transitiontemperature, used for actuation, is in the range of 20 C to 80 C. (3)The polymer is biocompatible (does not invoke immune response) andbiodegradable over a controlled period of time. Biodegradation productsshould likewise be non-toxic. (4) SMPs which have hysteresis in themodulus temperature curve. This means that the thermal transition fromthe glassy to the rubbery state in the SMP is higher during heating thanit is during cooling, such that following in-vivo actuation the SMPremains in an elastomeric state. The amount of the hysteresis,determined by the shift in the transition temperature as measured byDSC, would be in the range of 5 to 50° C. This shift could be due tomelting of crystallinity responsible for the transition, absorption ofphysiological compounds which act as plasticizers, thermally inducedmixing or demixing of the SMP itself, or chemical changes induced duringactuation which change the Tg of the material. This property of the SMPwould be important for preventing damage to tissue and organs duringuse. (5) The SMP can be blended with a radiogical contrast agent such asbarium sulfate, tantalum oxide, etc. (6) The SMP can be made into a foamby traditional or porogen templating techniques. (7) The surface of theSMP device can be chemically functionalized or alternatively coated topromote the formation of a thrombus within the polymer structure. (8)The SMP can contain a dye suitable for adsorption of electromagneticradiation with wavelengths in the range of 300 to 1200 nanometers. Dyeswith adsorption peaks centered near 800 nm would be particularlysuitable.

The SMP is ideally made into an open cell foam structure with adistribution of pore sizes in the range going from tens of nanometers toca. 500 microns on the high end. The mean pore size should be in therange of 10 to 50 microns. Such a pore size and size distribution wouldbe optimal for a therapeutic device used to treat aneurysm in thefollowing regards: it would promote the rapid aspiration of blood intothe device during expansion, including all components necessary forthrombus formation; it would allow for the making of foam structureswith high expansibility (low density); pore size and distribution can beused also to help control the recovery forces imposed by the device onthe aneurysm wall during expansion. The expansibility (Finalvolume/initial volume) of the foams claimed here are in the range of 200to 20000%, or expansion ratios of 2 to 200.

Referring now to FIG. 3, an example of SMP foam actuator is illustrated.The SMP foam actuator designated by the reference numeral 300 is shownafter being heated to 70 C, compressed, and cooled to room temperatureunder compression. The same SMP foam actuator designated by thereference numeral 300′ is shown after 5 seconds at 70 C followed bycooling to room temperature. The SMP foam actuator 300/300′ is an opencell foam composed of a polyurethane SMP. The foam is made using a 10%solution of SMP in DMSO impregnated into a pressed cube of sucrosecrystals, followed by solvent removal, extraction of the sucrose withwater, then dried. The SMP foam actuator can be made by a variety oftechniques including: (1) Porogen templating, (2) Chemical blowing, (3)Solvent (physical) blowing, (4) Gas blowing, (5) Freeze drying SMPsolutions, (6) High inverse phase emulsion process, or any combinationof the above techniques.

The SMP actuator can be expanded by various mechanisms for actuationbased on movement through a thermal transition. The mechanisms includeoptical heating, convective heating using a heat transfer medium,electrical resistance heating, inductive heating, x-ray inducedreaction, and by exposure to biologically compatible solvents which caninduce a change in the SMP thermal transitions when absorbed.

Referring now to FIG. 4, a system for optical heating using optic fibersto transport light energy to the SMP actuator as shown schematically.The system is designated generally by the reference numeral 400. FIG. 4is a schematic overview of an ischemic stroke treatment system 400.Laser light from laser 401 is transmitted through a multimode opticalfiber 402, a fiber coupler 403, an extension fiber 404 that enters thesterile surgical field, and a fiber pusher 405 with the SMP actuator 406at the distal tip of the central tube and inner catheter 410. Separatefibers are used to actuate the central tube tip and the inner cathetertip for independent control. A small amount of laser light is reflectedfrom the fiber-coil interface back through the coupler 403 into thephotodetector 407. Source fluctuations may be monitored by the sourcephotodetector 408. As the laser light heats the SMP 406 in the distaltip of the catheter, the umbrella deploys. As an optional designfeature, detection of the actuation can be fed back to the operator (orcomputer) 409. The SMP 406 movement causes the reflected signal todecrease. The changes in the reflected signal can be used to control thedriving current of the laser 401 or to alert an operator of the statusof the actuator 406 (e.g., open or closed). The light can be absorbed bya suitable dye, which is incorporated into the SMP actuator uniformly,or in a gradient engineered to provide for even heating throughout theactuator geometry.

Optical heating may also be accomplished by placing the light absorbingdye in an elastomeric coating on the surfaces of the SMP actuator or inan aqueous media which is in contact with the SMP device. Opticalheating is preferable from the standpoint that most of the energyapplied is used to heat the SMP, minimizing thermal damage to the bloodor tissue.

Convective heating may also be used for actuation of the SMP end bypumping a heated saline solution through the interstitial space betweenthe inside of the guide catheter and the outside of the second catheterwith the SMP actuator end. This approach can be combined withfiber-optic heating to boost the temperature of the saline to a neededlevel should cooling during transport through the catheter be a problem.

Inductive heating can be accomplished by filling the SMP withmicroparticles or nanoparticles of a material which can selectivelyabsorb RF radiation, converting it to heat. By having an evendistribution of particles in the SMP actuator and applying a uniformfield the SMP can be quickly and evenly heated for actuation.

An SMP foam occlusion device as described above has the properties ofbeing capable of catheter delivery, be easily and accurately positioned,have rapid and controlled expansion from a small initial size to a sizeand shape approximately that of the aneurysm or arteriovenousmalformation (AVM) being stabilized, be made of biocompatible materials,stimulate the bodies own repair mechanisms for the aneurysm or AVM, anddisappear without causing further injury as the vascular lumen repairsitself. The high expansibility of the device allows for treatment with asingle or relatively small number of devices versus the current need formany (tens) coil type devices. While the SMP foam has fairly lowmodulus, the strength of the foam is sufficient to prevent it from beingremoved from the aneurysm due to blood flow in the adjoining lumen. Thesystem of the present invention also allows for the removal of the SMPfoam device via the delivery catheter should there be a problem withplacement.

Referring now to FIGS. 5, 6, 7, and 8, different foam device systems areillustrated. The systems are designated generally by the referencenumerals 500, 600, 700, and 800 in the four figures. In FIGS. 5 and 6the SMP foam systems 500 and 600 are used to occlude and prevent furtherexpansion of aneurysm 501. In FIG. 7 the SMP foam system 700 is used toocclude and prevent further expansion of arteriovenous malformation 701.In FIG. 8 the SMP foam system 800 is used to occlude and prevent furtherexpansion of an enlarged capillary 801 shunting blood flow betweenarteries and veins.

The therapeutic devices 500, 600, 700, and 800 are deliveredendovascularly via catheter. The primary method for placement of thedevices 500, 600, 700, and 800 is via radiology. The devices 500, 600,700, and 800 have sufficient radio-contrast through the use ofradiopaque fillers or due to other aspects of composition. Other toolsfor determining placement include fiber-optic based imaging technologiessuch as OCT, etc.

The SMP foam devices 500, 600, 700, and 800 are released from thecatheter or guide wire either during actuation due to expansion awayfrom an interlocking geometry or following expansion through a secondactuation event. The foam is mechanically attached to the guide wire orcatheter and upon expansion, is released from the mechanical interlock.The collapsed device is shown in the expanded foam and variousgeometries that may be useful for the mechanical interlock. Other typesof release mechanisms can be used for the SMP foam device based on thechange in geometry of SMP and SMA devices on the catheter tip, todissolution of a bonding material, to galvantic erosion of a connector,etc.

Once the SMP foam device has been placed, it is important that is staysin position and does not get pushed out into the channel with thedesired blood flow pattern. There are a number of ways that the devices500, 600, 700, and 800 can be held in place. First, the device can holditself in place when it is situated in an aneurysm in which the aneurysmcavity is larger than the aneurysm opening. Upon thrombosis within thefoam, it will be very difficult for the foam device to be pushed out. Asecond method for holding the device into that cavity is through theaction of a diaphragm or other geometry which covers the aneurysmopening. In the case of the occlusion of a vascular shunt, the foamgeometry is made longer and tends to hold it in place both by thetapered geometry of the vascular lumen and the hydrostatic pressure ofthe blood flow. Thrombosis of the blood within the foam will also helpto hold it in place. A secondary device such as an SMP stent or coilstructure can also be used to provide additional support.

Referring now to FIG. 9, a collapsed device 900 is shown. The collapsedSMP foam device 900 may be connected at the end of a guide wire or othersystem fro delivery. The SMP foam device 900 is placed in the desiredlocation. For example, this is accomplished by delivering the SMP foamdevice 900 through a catheter using a guide wire.

Referring now to FIG. 10, an expanded foam (actuated) device 100 isshown. For example the device 1000 can be expanding it inside theaneurysm and occlude the aneurysm. The SMP foam device 1000 isexpandable from 100% to 10000%. The SMP foam device 1000 is actuated byone of several means including electromagnetic energy deliveredoptically. The SMP foam device 1000 can be used to occlude part or allof a lumen, aneurysm, or artiovascular malformation. The expanded SMPfoam device 1000 can be releasing from the end of a guide wire. Theguide wire can then retracted through the catheter. The catheter canthen be retracted from the artery.

Referring now to FIG. 11, examples of guidewires having variousgeometries 1101, 1102, 1103, and 1104 are shown that may be useful forthe mechanical interlock connecting the SMP foam to the end of a guidewire. The guidewire 1101 has a reduced diameter section near its distalend. The guidewire 1102 has a conical reduced diameter section near itsdistal end. The guidewire 1103 has a spherical expanded diameter sectionnear its distal end. The guidewire 1104 has a reduced diameter sectionand an expanded diameter section near its distal end.

Referring now to FIG. 12, another embodiment of the present invention isshown for retrieving a misplaced foam device. This embodiment isdesignated generally by the reference numeral 1200. The guidewire 1209that is normally used for delivering a SMP foam device includes a secondSMP (or other type) device 1201. The second SMP device 1201 can beseparately expanded.

The various components of the system 1200 include a delivery catheter1205, an inner catheter 1206 containing optical fibers 1207 and with aflaring SMP distal tip 1208, a guide wire 1209 with optic fiber 1210,and a SMP gripper/release device 1211. The misplaced SMP foam device1202 is shown located in an aneurysm 1212. The secondary SMP device 1201is at the distal end of the guidewire 1209 and can catch the misplacedfoam 1202 and draw it back toward the catheter 1205. An alternate devicewould allow the SMP foam to be gripped on each side and stretched toform a thinner cylinder for withdrawal.

In operation, the guidewire 1209 is extended through the misplaced SMPfoam. The second SMP device 1201 is expanded resulting in the misplacedfoam 1202 being gripped between the distal end 1203 of the guidewire1209 and the distal end of the second SMP expandable device 1201. Thefoam 1202 is then drawn back into the delivery catheter 1205 or simplyremoved by removable of the entire assembly while being gripped. Thesystem 1200 facilitates withdrawal of a misplaced device.

While the invention may be susceptible to various modifications andalternative forms, specific embodiments have been shown by way ofexample in the drawings and have been described in detail herein.However, it should be understood that the invention is not intended tobe limited to the particular forms disclosed. Rather, the invention isto cover all modifications, equivalents, and alternatives falling withinthe spirit and scope of the invention as defined by the followingappended claims.

What is claimed is:
 1. An endovascular therapy system comprising: adelivery wire; an open-cell polyurethane shape memory polymer (SMP) foamcoupled to the delivery wire; and a flaring SMP distal tip to couple tothe delivery wire proximate to the SMP foam; wherein the SMP foam isconfigured to transform from a collapsed state to an expanded state inresponse to thermal stimulus; wherein the flaring SMP distal tip isconfigured to transform from a collapsed state to an expanded state inresponse to at least one of heat, optical heat, convective heat,electrical resistance heat, inductive heat, and exposure to a solvent;wherein (a) the flaring SMP distal tip has a maximum width in theflaring SMP distal tip's expanded state, and (b) a proximal portion ofthe SMP foam has a maximum width in the SMP foam's collapsed state thatis narrower than the SMP distal tip's maximum width in the flaring SMPdistal tip's expanded state; wherein the flaring SMP distal tip isconfigured to flare outwards when the flaring SMP distal tip transformsfrom the collapsed state to the expanded state.
 2. The system of claim1, wherein the flaring SMP distal tip is configured to flare outwardsinto a frustoconical formation that expands outwards distally.
 3. Thesystem of claim 1, wherein a middle portion of the SMP foam has amaximum width in the SMP foam's expanded state that, when unimpeded by avessel, is greater than or equal to the SMP distal tip's maximum widthin the flaring SMP distal tip's expanded state when the SMP distal tipis unimpeded by the vessel.
 4. The system of claim 3, wherein (a) theflaring SMP distal tip has a maximum width in the flaring SMP distaltip's expanded state that is wider than a maximum width of a deliverycatheter channel the flaring SMP distal tip is configured to be deployedfrom, and (b) the flaring SMP distal tip has a maximum width in theflaring SMP distal tip's collapsed state that is narrower than themaximum width of the delivery catheter channel.
 5. The system of claim 1comprising a detachment device configured to decouple the SMP foam fromthe flaring SMP distal tip.
 6. The system of claim 5, wherein thedetachment device decouples the SMP foam from the flaring SMP distal tipin response to galvanic corrosion.
 7. The system of claim 1 comprising asecond expandable device, coupled to the delivery wire, having acollapsed state and an expanded state to withdraw the SMP foam from aphysical anomaly.
 8. The system of claim 7, wherein the SMP foam iscoupled to the delivery wire proximal to the second expandable device.9. The system of claim 1 comprising an optic fiber.
 10. The system ofclaim 1, wherein the SMP foam and the flaring SMP distal tip, whencoupled together, are configured to expand non-simultaneously.
 11. Thesystem of claim 1 comprising a heating system configured to couple tothe delivery wire, wherein the heating system includes at least one of afiber optic cable configured to produce optical heating, an electricalwire configured to produce electrical resistance heating, and a lumenconfigured to deliver a fluid to produce convective heating.
 12. Anendovascular therapy system comprising: a delivery wire; a polyurethaneshape memory polymer (SMP) foam coupled to the delivery wire; and aflaring shape memory (SM) element to couple to the delivery wireproximal to the SMP foam; wherein (a) the SMP foam and the flaring SMelement each transforms from a collapsed state to an expanded state; (b)the flaring SM element has a max width in the flaring SM element'sexpanded state that is wider than a max width of a proximal portion ofthe SMP foam in the SMP foam's collapsed state; and (c) the flaring SMelement flares outwards when transforming from the collapsed state tothe expanded state.
 13. The system of claim 12, wherein the flaring SMelement includes at least one of a SM alloy and a SMP.
 14. The system ofclaim 13, wherein the flaring SM element flares outwards into afrustoconical formation with a base of the frustoconical formationproximal to a tip of the frustoconical formation.
 15. The system ofclaim 14, wherein (a) the flaring SM element has a maximum width in theflaring SM element's expanded state that is wider than a maximum widthof a delivery catheter delivery channel the flaring SM element isconfigured to be deployed from, and (b) the flaring SM element has amaximum width in the flaring SM element's collapsed state that isnarrower than the maximum width of the delivery catheter channel. 16.The system of claim 15 comprising a detachment device configured todecouple the SMP foam from the flaring SM element.
 17. The system ofclaim 16, wherein the SMP foam and the flaring SM element are configuredto expand non-simultaneously.
 18. An endovascular therapy systemcomprising: a delivery wire; a polyurethane shape memory polymer (SMP)foam coupled to the delivery wire; and a flaring shape memory (SM)element configured to couple to the delivery wire proximal to the SMPfoam; wherein (a) the SMP foam and the flaring SM element eachtransforms from a collapsed state to an expanded state; (b) the flaringSM element has a max width in the flaring SM element's expanded statethat is wider than a max width of a proximal portion of the SMP foam inthe SMP foam's collapsed state; and (c) the flaring SM element flaresoutwards when transforming from the collapsed state to the expandedstate.
 19. The system of claim 18, wherein the flaring SM elementincludes at least one of a SM alloy and a SMP.
 20. The system of claim19, wherein the flaring SM element flares outwards into a frustoconicalformation with a base of the frustoconical formation proximal to a tipof the frustoconical formation.